Andrea Hinwood (1), Jane Heyworth (2), Helen Tanner (1), Clint McCullough (3)

  1. Centre for Ecosystem Management, Edith Cowan University
  2. University of Western Australia
  3. MiWER

Understanding Coal Pit Lake Resources within the Collie Basin Project

Funding: Department of Water (Western Australia) and Australian Government’s “Water for the Future” initiative


Government and community stakeholders have expressed concerns about how open cut mining operations may affect human health and wellbeing through modified surface and groundwater regimes and their follow-on effects on environmental contamination and disease propagation. This project used Collie as a case-study to investigate how the formation of pit lakes may degrade or even improve health outcomes for mining communities living with these legacies.

Sulfidic minerals release acidity and metals as AMD in Collie pit lakes


This project aimed to examine the possible impacts of human interaction with pit lakes. The project was conducted in three stages. The first was a literature review of the health effects of the aspects of pit lakes including chemical contamination, pH and also injury. The second stage of the work attained an understanding of how and how frequently the community was exposed to the pit lakes leading to the third stage, an assessment of the risks of exposure and health impacts. Stage 3 produced a screening health risk assessment identifying risks, management strategies, including management trigger levels to ensure the protection of human health.

Swimming in Black Diamond found to pose risk of amoebic meningitis – see NEWS story

What we did

Stage 1:  Literature review of historic and new Collie pit lake characteristics, data collation of existing information and assessment of health impacts of identified parameters.

This stage required the compilation of existing data on the chemical, physical and biological aspects of Collie pit lakes from the peer-reviewed and available grey literature. As there was little data publicly available on Collie pit lakes, this data compilation made extensive use of unpublished MiWER data. Project members from the MiWER team have an extensive dataset on water quality of most Collie pit lakes extending back more than a decade and also collected new data specifically for the health study. In addition, existing monitoring data was used to determine concentrations of relevant parameters and their likely health effects. The literature review outlined likely health effects associated with water temperature and other issues such as chemical injury. The data collated in Task 1 were used to identify potential chemical and biological human health risks associated with pit lakes in Collie. A further literature review also examined physical risks such as injury, water temperature and drowning.  

Stage 2:  Community Survey

To assess the use and perceived issues of using pit lakes a community survey was undertaken via administration of a postal questionnaire. The questionnaire was focussed on finding out how many people use the pit lakes, the purposes for which they use the lake, how often they use the lakes and for how long they have used the lakes and how they would like to use the lakes. We also obtained data on health issues that may be associated with pit lake water and other potential confounding factors. The questionnaire was designed based on the literature review. The population of Collie and surrounds is 7,194 persons and we aimed to obtain information from approximately 10% of the population. As response fractions are often low 1,500 questionnaires were posted to a random sample of residents of Collie. The selection was based on the electoral roll. A reply paid envelope was provided. The data collected via questionnaire was analysed and the information informed the screening health risk assessment in Stage 3. A report on the questionnaire was then developed and provided the Department with a variety of information on actual and perceived issues associated with pit lakes in the area. 

Stage 3:  Screening Health Risk Assessment.

Health risk assessment is a systematic, transparent process of assessing the potential risks associated with exposure to environmental and physical parameters. It uses a standard methodology which is routinely accepted worldwide and provides managers with good information on how to prevent and minimise both actual and perceived risks. Based on Stages 1 and 2 human health risks were determined based on the likelihood of them occurring, the consequence if they occur and therefore an assessment of the significance of the risk. This process also enabled the development of triggers to manage issues to prevent risks from occurring. This stage also identified any issues that required further investigation.


  1. The potential for health impacts from recreational pit lakes use in the Collie Basin was assessed by a review of available literature; the results of a community-based questionnaire and a screening-level risk assessment. Three pit lakes were the subject of the assessment, Black Diamond, Lake Stockton and Lake Kepwari. Results of this assessment need to be considered in light of a small response to the questionnaire (20% of the survey population) and a paucity of good quality water quality characteristics. Some recommendations have been made to address the shortfall in the information.
  2. A review of the literature reveals that there is limited information on recreational use of pit lakes. Nothing was found on the potential for health impacts other than injury. Results from health studies of the effects of pH, temperature, clarity and water quality (both biological and chemical) in other settings suggest these can have a significant impact on health depending on the type of activities an individual undertakes and their underlying health status.
  3. Sixty-two percent of respondents to the community-based questionnaire used the lakes for recreational purposes. Most respondents were male aged >50 years and spent an average of 2 days per month at the lakes in the warmer months of the year. There were few respondents who recreated at the lakes all year round. A fifth of respondents had young children who visited the lakes. Most respondents who visited the lakes visited Black Diamond and Lake Stockton and while Lake Kepwari was closed to the public, nearly 30% reported visiting and undertaking water-based activities at the Lake. Most respondents reported swimming, wading and picnicking as the most popular recreational pursuits.
  4. Thirty eight percent of respondents reported one or more health effects following use of the pit lakes. It must be noted that no information was collected on pre-existing health status. Of the symptoms reported, sore eyes were the most common followed by skin rashes and irritations. Only 3% of respondents reported symptoms every time they used the lakes and this was reported most often in relation to Black Diamond. Acidity could lead to such symptoms and potentially affect sensitivity to metals from skin barrier disruption caused by low pH.
  5. Water quality of the pit lakes is variable with most parameters measured at detection limits well above current ANZECC/ARMCANZ (2000) recreational water quality guidelines for swimming. To date, assessment of water quality at the lakes has been undertaken with an environmental focus. Water samples have been used to assess remediation techniques and ecological values. This has reduced the ability to comment on whether water quality parameters do or do not present health risks. An ad hoc collection of water samples in 2010 with analysis using detection limits below ANZECC/ARMCANZ (2000) guidelines was undertaken during the preparation of this report. These results differed from existing data with fewer metals at elevated concentrations. It is recommended that future monitoring should be undertaken using detection limits suitable for assessing health. These can be found for each physical and chemical parameter in the Australian Drinking Water Guidelines (ANZECC/ARMCANZ 2000).
  6. Of the small amount of data available (from the MiWER database) to assess the potential for health effects, mercury concentrations at Black Diamond are significantly higher than recreational water quality guidelines. Arsenic concentrations at Lake Stockton were also elevated and aluminium is above ANZECC/ARMCANZ (2000) recreational water quality guidelines at all three lakes. Iron and manganese were above recreational water guidelines at Lake Kepwari. The limited data from the analysis undertaken in April 2010 indicates that current mercury and arsenic concentrations are below ANZECC/ARMCANZ guidelines. Aluminium concentrations are elevated and above guidelines values at all three lakes.
  7. No vector-borne disease potential has been identified and the presence of the nuisance midge Ceratopogonidae is not viewed as a significant health risk. Respondents to the questionnaire did not indicate this was an issue of concern. The potential exists however for biological factors and in particular microbial contamination to be an issue with the pit lakes. Future monitoring and management should address this issue.
  8. A screening-level health risk assessment was conducted for mercury, aluminium, manganese and arsenic concentrations in surface water. It found that the frequency of recreational use was too low to result in significant health effects despite the elevated concentrations. The potential for health impacts from exposure to mercury increases significantly if seafood is consumed. Because of the low response fraction to the survey, we cannot estimate the true frequency and duration of use of the lakes with any certainty. These results must also be treated with caution due to the lack of information on other parameters such as dermal absorption rates and inhalation of water whilst swimming or a comprehensive water quality data set. Children would be a sensitive subgroup and it is felt that measures to reduce exposures in this group should be considered. Further, the metals concentrations in surface water are above acceptable recreational water quality guidelines and hence management may be required once this is confirmed by more comprehensive and targeted monitoring This will be important if the potential exists for marron farms or aquaculture where the risks of metals uptake are high.
  9. There are still many questions about the potential for health risks. To clarify whether current concentrations are impacting on health it is recommended a comprehensive water quality monitoring program be implemented with appropriate detection limits for metals and includes testing for micro-organisms, biological pathogens, and vector-borne diseases. To ensure that exposure to metals is not a significant issue, a short term human exposure study could assist in assessing human health risks and firm up the results of the screening health risk assessment.
  10. If further monitoring of the water quality in the pit lakes confirms elevated mercury, we advise the Department of Water to develop a communication plan to advise users of the potential issues. As noted, the recent samples analysed in April 2010 for mercury and arsenic concentrations are below recreational water guidelines
  11. Respondents to the survey were concerned about the management of the pit lakes with sixty percent wanting some form of active management by the placement of facilities such as toilets. Nearly eighty percent want the lakes used for water-based recreational areas.
  12. Of urgent attention is the need to address management of the lakes with the provision of appropriate facilities such as toilet blocks with cleaning and rubbish bins and collection. This would reduce the risks of injury from broken glass bottles and other wastes left in the areas. Installation of toilet facilities would reduce the potential for health effects from faecal contamination.


  • Hinwood, A., Heyworth, J., Tanner, H., McCullough, C., and Lund, M. (2011) Water Quality of Mine Void Pit Lakes Used for Recreation. Epidemiology 22 (1), S296 link
  • Hinwood, A.; Heyworth, J.; Tanner, H. & McCullough, C. D. (2012). Recreational use of acidic pit lakes – human health considerations for post closure planning. Journal of Water Resource and Protection. 4: 1,061-1,070. link
  • Hinwood, A. L.; Heyworth, J.; Tanner, H. & McCullough, C. D. (2010). Mine Voids Management Strategy (II): Review of potential health risks associated with Collie pit lakes. Department of Water Project Report MiWER/Centre for Ecosystem Management Report 2010-11, Edith Cowan University, Perth, Australia. 111pp. Unpublished report to Department of Water. PDF